The invention relates to an oil-in-water emulsion for cold rolling light metals, in particular aluminum and aluminum alloys, containing for example polyisobutylene as hydrodynamic film former, alkylmonocarboxylic acid esters as reaction layer former, polyethoxylated sorbitanoleates as emulsifier, unsaturated, long chain alkylmonocarboxylic acids as inhibitor against hydrogen embrittlement and rusting, hexamethylenetetramine as stabilizer, fungicide and bactericide and deionized water.
Compared with oil-based rolling lubricants oil-in-water emulsions, because of the larger heat of vaporization of water, permit much better cooling and consequently a much larger reduction per pass and/or higher rolling speed. Besides these purely economic factors which help achieve greater efficiency, it must also be mentioned that aqueous folling lubricants produce much less severe problems due to waste fumes and are less dependent on mineral oil. For this reason many trials have already been carried out in the light metal industry, in particular in the aluminum industry, with a view to using oil-in-water emulsions for cold rolling strip.
Revealed in the German Auslegeschrift No. 26 32 142 is an oil-in-water emulsion for cold rolling light metals, containing alkylmono carboxylic acid esters as reaction layer former, polyisobutylene as hydrodynamic film former, polyethoxylated sorbitanoleates as emulsifier, unsaturated, long chain alkylmonocarboxylic acid as inhibitor against hydrogen embrittlement and rusting, hexamethylenetetramine as stabilizer, fungicide and bactericide, balance deionized water.
A basic disadvantage with the oil-in-water emulsions representing the state of the art is that the freshly formed surface produced by rolling reactants with water within the space of only a few seconds. This corrosive attack of the surface by the aqueous phase leads to undesirable stains on the surface of the strip. The poorer surface quality of the strip or foil due to these water stains is unacceptable for many applications. With the known oil-in-water emulsions it is therefore absolutely essential that the emulsion is removed as completely as possible, immediately after the strip exits from the rolls, for example by blowing with compressed air.